Particularly popular regularization techniques are variational methods [1]}, [2]}. These methods recover regularized solutions \(x_\alpha ^\delta \)  as global minimizers of the Tikhonov functional
\( \mathcal {T}_{\alpha , y^\delta }(x) \frac{1}{2} {\mathbf {K}x- y^\delta }^2 + \alpha \mathcal {R}(x) \,.\) 
